1. Field of the Invention
The present general inventive concept relates to an electrophotographic toner and a method of preparing the same.
2. Description of the Related Art
In an electrophotographic process or an electrostatic recording process, a developer used to visualize an electrostatic image or an electrostatic latent image may be classified into a two-component developer formed of toner and carrier particles or a one-component developer formed of only toner. The one-component developer may be classified into a magnetic one-component developer or a nonmagnetic one-component developer. Fluidizing agents such as colloidal silica are often added to the nonmagnetic one-component developer to increase a fluidity of the toner. Typically, coloring particles, obtained by dispersing a coloring agent such as carbon black or other additives in a latex, are used in the toner.
Methods of preparing toner include pulverization and polymerization. In the pulverization method, the toner is obtained by melting and mixing synthetic resins with coloring agents and, if required, other additives, and by pulverizing the mixture and sorting the particles until particles of a desired size are obtained. In the polymerization method, a polymerizable monomer composition is manufactured by uniformly dissolving or dispersing various additives, such as a coloring agent, a polymerization initiator and, if required, a cross-linking agent and an antistatic agent, in a polymerizable monomer. Then, the polymerizable monomer composition is dispersed in an aqueous dispersive medium, which includes a dispersion stabilizer, using an agitator to shape minute liquid droplet particles. Subsequently, a temperature of the mixture is increased and suspension polymerization is performed to obtain polymerized toner having coloring polymer particles of a desired size.
In an image forming device, such as an electrophotographic device or an electrostatic recording device, an image is formed by exposing an image on a uniformly charged photoreceptor to form an electrostatic latent image, attaching toner to the electrostatic latent image to form a toner image, transferring the toner image onto a transfer medium such as transfer paper, or the like, and then fixing the toner image on the transfer medium by any of a variety of methods, including heating, pressurizing, solvent steaming, and the like. In most fixing processes, the transfer medium with the toner image disposed thereon passes through fixing rollers and pressing rollers, and the toner image is fused to the transfer medium by heat and pressure.
Images formed by an image forming apparatus such as electrophotocopier should satisfy requirements of high precision and accuracy. Conventionally, toner used in an image forming apparatus is usually obtained by using the pulverization method. In the pulverization method, color particles having a large range of toner particle size distribution are formed. However, in order to obtain satisfactory developing properties, there is a need to sort the coloring particles obtained through pulverization according to size so as to reduce the particle size distribution. However, it is difficult to precisely control the particle size and the particle size distribution using a conventional mixing/pulverizing process in the manufacture of the toner which is suitable for an electrophotographic process or an electrostatic recording process. Also, when preparing a fine particle toner, the toner preparation yield is adversely affected by the sorting process. In addition, there are limits to the change/adjustment of a toner design in order to obtain desirable charging and fixing properties.
Accordingly, polymerized toner, the size of particles of which is easy to control and which does not need to undergo a complex manufacturing process such as sorting, has been highlighted recently. When toner is prepared through polymerization, polymerized toner having a desired particle size and the particle size distribution may be obtained without pulverizing or sorting.
In this regard, a viscosity of the polymerized toner needs to be decreased. In addition, viscosity of the polymerized toner needs to be optimized so that the polymerized toner is easily peeled off from paper and is prevented from hot-offset development. The viscosity of the polymerized toner may be optimized by controlling a degree of crosslinking and by using a low-melting point/low-viscosity wax. However, if the low-melting point/low-viscosity wax is used to increase glossiness, the wax dispersed in the toner becomes fluidic during a coalescence at a temperature higher than the melting point of the wax after the agglomeration, and thus, the wax is exposed on a surface of the toner. In addition, small particulate toner (<D16) having lower compatibility with a resin than large particulate toner (>D16) has a low amount of wax, and thus an image quality may be deteriorated due to stains formed during the development process.